Date: 01.04.2026
What is a season, really? Scientists seek more precise language to describe changes in lakes
What exactly is a season? And what does seasonality mean in freshwater ecosystems? At first glance, the answer seems simple: spring, summer, autumn, winter. But a closer look reveals that these terms are far less straightforward than they appear.
This question was addressed by an international team of limnologists, including Petr Znachor from the Biology Centre of the Czech Academy of Sciences, in a new review article published in Limnology and Oceanography Letters. The authors show that the concept of a “season” can have very different meanings in different parts of the world and across different types of lakes. In temperate regions, seasons are typically associated with the four traditional divisions of the year. In the tropics, however, wet and dry periods may be more relevant. Even within a single lake, a “season” can be defined in multiple ways, for example, according to water temperature, the presence of ice cover, thermal stratification, hydrological regime, or the seasonal development of plankton communities.
The article reviews how the terms “season” and “seasonality” are used in limnological literature and proposes a framework that helps distinguish more precisely among different types of seasons and their ecological significance.
This is not merely a matter of terminology. In the context of ongoing climate change, lake seasons are shifting. Ice cover duration is shortening, the period of summer stratification is lengthening, and the timing of biological processes is changing. However, if we are unable to clearly define what we are measuring, it becomes difficult to compare changes across regions or to predict their impacts on the functioning of aquatic ecosystems.
The new study highlights that more precise use of terminology can benefit not only scientists, but also water managers and anyone concerned with the effects of global change on freshwater ecosystems.
Figure: An example of seasons conceptualized as cyclical variables in three types of lakes: (a) a temperate dimictic lake, (b) a tropical meromictic lake, and (c) a permanently ice-covered Antarctic lake. Astronomical seasons (discrete, static) are shown in the inner circle, divided by solstices and equinoxes. Seasonality of day length (continuous, static) is represented by an orange gradient in the second circle. Lake stratification intensity (continuous, dynamic) is shown in the outer circle: blue indicates mixed conditions, while shades of red correspond to the magnitude of density differences. Ice cover (discrete, dynamic) is marked in the outer circle during periods when it is present.
Publication
Lewis A.S. L., D.C. Richardson, D.W. Howard, C.C. Carey, B.M. Kraemer, Y. Amitai, S. Bansal, E. de Eyto, H.P. Grossart, K. K. Hoffman, R. A. Hovel, L. Knoll, I. A. Oleksy, A. B. Santoso, M. Schmid, R. Schwefel, D. Straile, X. Sun, G. A. Weyhenmeyer, W. M. Woelmer, S. Wollrab & P. Znachor (2026): Seasons and seasonality in lakes: A synthesis amid global change. Limnology and Oceanography Letters, 11(2), e70116. https://doi.org/10.1002/lol2.70116
